Sand Diver, Synodus intermedius
Sand Diver, Synodus intermedius. Underwater photograph taken in coastal waters of Yal-Ku, Quintana Roo, April 2016. Photograph courtesy of Juan Rojo, Akumal.
The Sand Diver, Synodus intermedius, is a member of the Lizardfish or Synodontidae Family, that is also known as the Common Sand Diver and the Sand Diver Lizardfish and in Mexico under a variety of names including Chile Manchado, Doncella, Guaripete, Guaripete Amarillo, Guavina, Huavina, Jagarto, Lagarto, Lagarto Gigante, Lagarto Manchado, Lagarto Mato, and Manuelito. Globally, there are thirty-seven species in the genus Synodus, of which eleven are found in Mexican waters, six in the Atlantic and five in the Pacific Ocean.
The Sand Diver has a very elongated, cylindrical or cigar-shaped elongated body. Their body varies in color from brown, to reddish, to silver with red, yellow or blue markings and they have 9 to 13 dark hourglass brown bars along the mid-sides with the last bar being an inverted “Y”. They have thin gold or blue lines along the upper body, and a broken white stripe along the lower flank and a broken white stripe along the lower flank. The anal fin is yellow, the caudal fin has 3 to 5 dark bards across both lobes, and the pelvic fins are golden yellow. There is a black blotch at the top corner of the gill cover. Their head is a long triangularly pointed snout with relatively small eyes with a lower jaw that extends past the upper jaw and a large wide mouth that extends well past the eyes and is equipped with numerous small needlelike teeth. Their adipose fin is small; their anal fin has 11 rays and its base is shorter than than the dorsal fin base; their caudal fin is forked; their single dorsal fin has 11 or 12 rays and is located mid-body; their pectoral fins have 11 to 13 rays; and, their pelvic fins have 8 rays and are set behind the pectoral fins. They are covered with small scales.
The Sand Diver is a demersal species is found on or near the seabed in sandy areas among boulders or in sandy corridors in reefs, but they also rest on the tops of reef structures at depths up to 320 m (1,050 feet), but seldom near shore. They reach a maximum of 46 cm (18 inches) in length and 1.0 kg (2 pounds 3 oz) in weight. They are a lie-in-wait ambush predators, spending the majority of their time submerged in the substrate with only their head and eyes exposed. They primarily consume fish and smaller amounts of crabs, cephalopods and shrimp. They utilize camoflage with the ability to change colors to blend into the substrate as their primarly defense mechanism. Reproduction is oviparous being dioecious with separate males and females; fertilization is external with the eggs receiving no parental care. Males have elongated dorsal fin rays and a long pelvic fin filament.
The Sand Diver is a resident of all Mexican waters of the Atlantic Ocean including the Gulf of Mexico and the east coast of the Yucatán Peninsula in the Caribbean.
The Sand Diver is most likely confused with the Inshore Lizardfish, Synodus foetens (lack dark hourglass bars on the sides), the Largespot Lizardfish, Synodus macrostigmus (lack dark hourglass bars on the sides), the Offshore Lizardfish, Synodus poeyi (lack dark hourglass bars on the sides), Red or Redbarred Lizardfish, Synodus synodus (red bars) and the Snakefish, Trachninocephalus myops (blunt short shout with an oblique mouth).
From a conservation perspective the Sand Diver is currently considered to be of Least Concern, with stable, widely distributed populations. They are caught as a bycatch of shrimp trawlers where they are discarded and by recreational and subsistence fishermen. They are known to be preyed upon by the newly introduced highly invasive Red Lionfish, Pterois volitans. They are utilized by the aquarium trade as a nominal level.